HTLV III infection, now referred to as HIV infection, commonly results in AIDS (Acquired Immune Deficiency Syndrome). Reported increasing numbers of AIDS patients in the United States has caused the disease to be recognized as approaching epidemic proportions with no known cure or vaccine. The occurrence of AIDS has been increasing primarily in Europe and African countries of the world as the disease is transmitted through sexual activity, drug abuse, contaminated organs in transplantation procedures and by blood transfusions. Other strains of the HIV such as HTLV IV are developing through mutation of this virus.
Separate tests for the presence of HIV antibody or HIV antigen have been developed by investigators, including scientists at the National Institute of Health (NIH). Assays for detecting HIV antibody in plasma and serum have received clinical approval for commercialization. Assays for detecting HIV antigen are known for research use but to our knowledge none has received clinical approval for commercialization. These tests separately and independently analyze the plasma, serum or blood cell culture supernatant of screened individuals for HIV antigen or human anti-HIV antibody content which binds the HIV antigen, see Anti-HIV Testing: Screening and Confirmation Tests, Medical Laboratory Products, April 1987, p. 16-18, for a recent review article comparing several such separate tests.
Human antibody develops in 4 to 6 weeks in 70-80% of the people exposed to HIV through sexual intercourse, blood transfusions, contaminated organs through transplantation or contaminated needles by drug abusers. The remaining 20-30% of exposed individuals who do not develop antibodies against the invading virus for a period of up to six months can remain undetected carriers in society. Therefore, if one is to effectively screen blood and organ donors, individuals, or blood products for containing the spread of AIDS, it is essential that the screening immunoassay be able to detect not only HIV antibody but also the HIV virus itself and/or infected cells carrying the virus.
Heretofore difficulty has been encountered with false-positive results which may occur due to nonspecific antibodies or to antibodies directed against normal cellular antigens in supporting cell cultures used to obtain supernatants containing viral particles in sufficient quantity as is generally necessary to overcome the less than desirable sensitivity of prior tests.
We are not aware of any investigational or clinical immunoassay for simultaneously detecting through analysis of a single moiety of a physiological fluid test specimen both members of a single binding pair such as anti-HIV antibody, the HIV organism or HIV infected blood cells, for instance, such as in a human blood sample. The assay embodying the invention successfully tests for both the virus, virus infected cells and antibodies which bind the HIV organism. The assay can be performed in a single vessel such as a microtiter plate well. Preferably, the patient's test sample comprises human plasma, i.e, whole blood from which all cells have been removed initially, or serum, i.e., plasma from which all clotting factors have been removed. The assay provides a result of "positive" or "negative" as the case may be, by enzyme immunoassay (EIA). The suitability of the use of the assay of this invention to identify AIDS infected patients is significantly greater than has been realized heretofore where an immunoassay tracks only antibodies to HIV in a physiological sample such as peripheral blood. The test result is achieved in approximately four hours.
Lysing of viral concentrates to release viral proteins prior to using electrophoresis to spread viral proteins, i.e., antigens, on polyacrylamide gel is known with respect to a Western, blot technique for confirming the, presence of only anti-HIV antibodies, not antigens, and is thus of no practical utility during that period of time prior to when no antibodies are present even though the patient has been infected with HIV. Similarly, the use of an HIV lysate as a solid phase protein adhered to a solid phase support, such as a microtiter plate formed of polystyrene, is known with respect to an ELISA technique for screening for anti-HIV antibodies, not antigens, during that period after HIV infection when no antibodies are present. However, it has not been recognized that the lysing of HIV in a specimen in contact with an antibody coated solid phase, in the presence of a known amount of HIV antigen prior to incubation of the test sample in the presence of biotinylated antibody comprising a member of a single binding pair, can provide for the relatively rapid, sensitive quantitative measurement of both antibody and antigen in a single test sample.